from datetime import datetime, timedelta
from typing import Any, Union
from jose import JWTError, jwt
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.orm import Session
from passlib.context import CryptContext

from app.core.config import settings
from app.db.session import get_db
from app.models.user import User

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24 * 8  # 8 days

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")

def create_access_token(
    subject: Union[str, Any], expires_delta: timedelta = None
) -> str:
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode = {"exp": expire, "sub": str(subject)}
    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

def verify_password(plain_password: str, hashed_password: str) -> bool:
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password: str) -> str:
    return pwd_context.hash(password)

async def get_current_user(
    db: Session = Depends(get_db),
    token: str = Depends(oauth2_scheme)
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(
            token, settings.SECRET_KEY, algorithms=[ALGORITHM]
        )
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
        
    user = db.query(User).filter(User.username == username).first()
    if user is None:
        raise credentials_exception
    return user

async def get_current_active_user(
    current_user: User = Depends(get_current_user),
) -> User:
    if not current_user.is_active:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user 